Crab contributions as an ecosystem engineer to sediment turnover in the Yellow River Delta

Abstract

Burrowing crabs are widely distributed and have large populations in estuarine wetlands. Crab excavation can have potentially significant bioturbation effects on the vertical structure of sediments, and the processes of nutrients deposition and mineralization. However, the effects of crab micro activities on the geochemical cycling processes of the whole estuarine ecosystems are not clear, specifically the contributions of burrowing crabs to sediment and nutrients turnover in coastal ecosystems. Due to the lack of knowledge on crab burrowing behavior and borrow morphology, it is difficult to accurately estimate the excavation and turnover volumes of crabs. Therefore, this study examined the bioturbation activity of the crab Helice tientsinensis in western Pacific estuary ecosystems by analyzing their burrow morphology and local sediment properties. The common burrow shapes of Helice tientsinensis were J- and Y-shaped burrows. Burrow morphological characteristics such as total burrow depth, curve burrow length, burrow volume, and opening diameter significantly differed among tidal zones. Crab carapace size, water depth, soil hardness, and bulk density were the main factors driving burrow morphology. Sediment excavation by crabs was ~50 times greater than the deposition of sediment into crab burrows. The net transported amounts of sediment (31.66–33.18 g·d-1·m-2) and nutrients (total nitrogen: 0.075–0.090 g·d-1·m-2, total carbon: 3.96–4.55 g·d-1·m-2, and organic matter: 0.44–0.77 g·d-1·m-2) were mainly from the belowground sediment to the surface. These results highlighted the important role of crabs in sediment and nutrients cycling within coastal estuary ecosystems.

Tidal zone effects on the diet composition of leaf-eating crabs in natural mangrove communities: a stable isotope analysis

“…They participate in the trophic dynamics of mangrove ecosystems through nutrient cycling, bioturbation, and as prey or predator (Bui and Lee, 2014;Medina-Contreras et al, 2022). Among benthic invertebrates in mangrove forests, leaf-eating crabs play a pivotal role as "ecosystem engineers" (Araujo et al, 2012;Gao and Lee, 2022;Medina-Contreras et al, 2022) because of their top-down role in food web energy flow (Swindells et al, 2017;Xie et al, 2022). Crab activities include feeding, burrowing, and crawling (Lee, 1997).…”

Effects of an Invasive Mud Crab on a Macroalgae-Dominated Habitat of the Baltic Sea under Different Temperature Regimes

“…Crabs and lobsters, for example, can aggressively interfere with access to food by other species and displace competitors through agonistic displays or direct engagement in combat [11]. Multiple decapod species exhibit digging behavior, producing burrows in soft-bottom habitats to avoid predators, escape environmental stress, or as housing during mating and molting [14,15]. Their burrowing promotes sediment turnover and intensifies the water-sediment exchange of gases, organic matter, and nutrients, affecting not only the physical-chemical conditions of the habitat but also the composition of resident micro-and macro-communities (e.g., [15][16][17][18][19]).…”

“…Multiple decapod species exhibit digging behavior, producing burrows in soft-bottom habitats to avoid predators, escape environmental stress, or as housing during mating and molting [14,15]. Their burrowing promotes sediment turnover and intensifies the water-sediment exchange of gases, organic matter, and nutrients, affecting not only the physical-chemical conditions of the habitat but also the composition of resident micro-and macro-communities (e.g., [15][16][17][18][19]). When present in vegetated habitats, such as seagrass meadows or macroalgal beds, decapods can shred blades and dislodge whole plants during their feeding and burrowing activities, thereby modifying the structure of these habitats (e.g., [20]).…”